Objective-C，如何正确地将十六进制编码为图像文件？ [英] Objective-C, How to properly encode hex to image file?

问题描述

我在我的应用程序中有一个方法，我想将十六进制值写入文件（实际上是从写入的字节创建一个映像）。我似乎无法弄清楚如何正确编码值来生成图像。任何建议，将不胜感激 - 谢谢。

   - （void）makeImage {
 
 @autoreleasepool {
 
 NSString * hexValues = @8950 ...//这些是组成图像文件的十六进制字节
 
 NSString * fileName = @image.png; 
 NSString * homeDir = [NSHomeDirectory（）stringByAppendingPathComponent：@Desktop /]; 
 
 NSString * fullPath = [homeDir stringByAppendingPathComponent：fileName]; 
 
 NSError * error = nil; 
 [lastLine writeToFile：完整路径原子化：NO编码：NSASCIIStringEncoding错误：& error]; 
 
 
  

解决方案

使用有损ASCII编码或UTF-8转换NSData中的NSString，然后您可以使用方法 - [NSData bytes]来获取原始字节。

使用for循环一次循环遍历2个字节，然后可以将您要上传的两个字节/字符复制到大小为3的char数组中（3包含\0，请确保使用00 来终止\0）然后你可以使用c函数

$ p $ long c ++ strtol（const char * str，char ** endptr，int base）;

将两个字节/十六进制转换为整数。

或者你可以写你自己的十六进制字符串为int，不需要终止\0。

I have a method in my app that I would like to write hex values into a file (essentially creating an image from the written bytes). I can't seem to figure out how to encode the values properly to produce the image. Any suggestion would be appreciated - thanks.

- (void)makeImage {

@autoreleasepool {

    NSString* hexValues = @"8950..." // these are the hex bytes that make up the image file

    NSString* fileName    = @"image.png";
    NSString* homeDir     = [NSHomeDirectory() stringByAppendingPathComponent:@"Desktop/"];

    NSString* fullPath = [homeDir stringByAppendingPathComponent:fileName];

    NSError* error = nil;
    [lastLine writeToFile:fullPath atomically:NO encoding:NSASCIIStringEncoding error:&error];

}

解决方案

You can convert the NSString in an NSData with lossy ASCII encoding or UTF-8, then you can use the method -[NSData bytes] to get to the raw bytes.

Use a for loop to loop through them 2 bytes at a time, you can then either copy the two bytes/characters you are upto into a char array of of size 3 (3 to include the \0, make sure you initialize it with "00" to get a terminating \0) you can then use the c function

long int strtol ( const char * str, char ** endptr, int base );

to convert the two bytes/hex to an integer.

Alternatively you can write your own hex-string to int that doesn't require a terminating \0.

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